There exist many known transducers from which an electrical signal is derived. Common examples are electrical resistances, and inductances, where an element by its deflection allows the generation of an electrical quantity.
The resistor transducer necessitates the contact of elements which results in friction. This not only causes unwanted wearing but also requires the initial threshold of force to overcome the friction. This may limit the applicability of the device where minute displacements are involved. Also, the threshold level which must initially be overcome will vary as a result of the wearing of the elements thereby causing varying outputs for the same displacement.
A solenoid transducer is an example of a well known inductive transducer. Usually, the devices involves a freely movable ferromagnetic core which is moved in an out of a coil to vary the inductance of the coil.